Kobeite-(Y)

 IMA-GP
Uranium 8.3.12.1
(Dana Classification Number)
(Images) 4/D.20-20
(Strunz ID)

Property Data Remarks
Named for: Kobe (Oyama-cho), Ohmiya town, Kyoto prefecture, Kinki region, Honshu island, Japan, its type locality, and its Yttrium content
Alternate
    Name(s):
  		•  
    Mineral Class:
    Oxides
      Oxides with metal:
    [metal:oxygen = 1:2 (MO2 and related compounds)]
        Kassite - Lucasite-(Ce) series
    		 
    Chemical
        Formula:    		 (Y,U)(Ti,Nb)2(O,OH)6     (?)  
    Chemical
        Composition:
    Hydrogen: (H) 0.32%
    Niobium: (Nb) 14.56%
    Oxygen: (O) 30.08%
    Titanium: (Ti) 22.51%
    Uranium: (U) 7.46%
    Yttrium: (Y) 25.08%
    		by weight
    Molecular
        Weight:    		 319.10 daltons (amu)
    Specific
        Radioactivity:

    (All radiation is for a 1 gram, fully aged specimen)

    Specific Activity Dose Rate
    Becquerels Curies milliRems/hour microSieverts/hour
    1.3352 × 1004 3.61 × 10-07 0.19 1.92

    Estimated Average Annual Exposure: 360 mRem (3.6 milliSieverts)
    Crystalography:
    System: Isometric - Cubic or orthorhombic
    Cell Dimensions: a: 5.021 Å
    Z: 1
    V: 126.58 Å3
    DenCalc: 4.19
    H-M Symbol:  
    Space Group: Cubic
    X-Ray Diffraction:
      By Intensity ( I/Io )    		 (1): 2.89 Å
    (0.8): 1.776 Å
    (0.7): 1.514 Å
    		 
    Habit:
  • Prismatic
  • Radial
  • Twins common in Kobe specimens. Coaxial in their major axis, 90° in their minor axis (see cross-sectional image above). Those from Hiroshima city are not twinned.
    		•   
    Cleavage: None  
    Fracture: Brittle - Conchoidal  
    Moh's
        Hardness:    		 5.5  
    Density: 4.6 grams/cm3
    Color: Brown, Brownish black, Dark brown, Black  
    Streak: Reddish brown to Dark brown  
    Luster: Vitreous - Resinous  
    Diaphaneity: Transparent to Translucent  
    Pleochroism:
    (x):  
    (y:)  
    (z:)  
    		 
    Ultra Violet
        Fluorescence:
    Long Wave:  
    Short Wave:  
    		 
    Magnetism: Non-magnetic  
    Occurance:
  • Granite pegmatites
    		•   
    Associated
        Minerals:    		 Fergusonite, K Feldspar, Thortveitite, Zircon These are minerals known to be found with Kobeite-(Y)
    Localities:

    Extremely rare

    Kobeite-(Y) Localities
    Notes:

    Somewhat radioactive a- and b-particles, g-rays.

    Usually metamict.

    At least some crystals from Kobe, Japan, are twinned, those from Hiroshima City, Japan, not twinned.

    Kobeite Images

    Specimen Top
    (001a) (001b) (001c)

    (lateral)
    (cross section)
    Shiraishi-yama, Kobe (Oyama-cho), Ohmiya town, Kyoto prefecture, Kinki region, Honshu island, Japan

    Specimen Notes

    Occurrence - The matrix rock appears to be consolidated volcanic ash.

    Crystals - The crystals from this one specimen are nearly all twinned. Three specimens from another collection from Hiroshima City, Japan, are not twinned. The significance of this is not known.

    The crystals also appear to occur in clusters. All the visable crystals are generally aligned to each other. All of the observable crystals have their long axis aligned to within about 20° of each other. The same appears true of the short axes of the crystals.

    Appearence -  

    Diaphaniety - The crystals of Kobeite are opaque.

    Luster - The surface luster is dull, earthy. This is suspected to be from the particles composing the matrix interfering with the growth of the Kobeite. The surfaces presented by freshly cleaved surfaces is vitreous.

     

    Color - The surface of the crystals appear to be brownish-black, while the freashly cleaved surfaces appear more black with little brown.

     

    Specimen Physical Properties
    Size   cm   cm   cm
    Weight: x grams    
    g-Radiation Level:   cmp   msieverts background: 20 cpm